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Evidence shows Grey Seals may be responsible for spiral seal injuries.

There is strong evidence that predatory behaviour by Grey Seals, rather than ship propeller injuries, is likely to be the main cause of spiral seal deaths, often referred to as “corkscrew seals”.

Sea Mammal Research Unit researchers observed a grey seal killing 5 young seals, leaving them with the distinctive spiral seal injuries. Combined with recent similar evidence from Germany, this suggests such behaviour may be more common and could explain the unusual clusters of injured seals found in Scottish waters.

This evidence does not completely eliminate ship propellers, but it is now less likely they are a key factor. Marine Scotland will continue to fund research into this issue.

Scottish Environment Secretary Richard Lochhead said:

“The clusters of ”corkscrew seal” deaths were unusual and worrying. In common with many of the creatures that live in our seas, seals are animals that are loved by the public.

“It is very important that we understand what caused these unusual deaths and we now have important evidence that natural predatory behaviour is likely to be the main cause, rather than ship propeller injuries as we first thought. This provides some reassurance for the shipping industry .

“This information will help to inform regulators, developers and others enabling them to take it into account in their activities. Marine Scotland will continue to monitor our seal population for further injuries and any evidence about the causes.”

Notes To Editors

In the period 2009-2014 (to October 2014), 86 seal carcasses were found in Scotland with unusual spiral injuries (corkscrew seals) the cause of which was then unknown. 

In response, Marine Scotland commissioned the Sea Mammal Research Unit (SMRU) at St Andrews University to investigate possible causes. Until late in 2014, the investigation suggested that certain types of ship propellers might be responsible for the injuries and, indeed, scale model tests appeared to confirm this. As a result, SMRU were funded to tag a number of grey seals in the Firth of Forth to examine potential interactions with shipping and, if possible, discover if any suffered the recorded spiral injuries as a result. 

During this work a number of examples of juvenile grey seals with typical spiral injuries were found but, unexpectedly, these were seen and recorded to be the result of adult grey seal predation.

The full report is available from : http://www.smru.st-and.ac.uk/documents/2162.pdf